1. Field of the Invention
The present invention relates generally to a thin film electroluminescent light source, and more particularly, is concerned with an integrated TFEL flat panel face and edge emitter structure for simultaneously producing multiple light sources
2. Description of the Prior Art
Electroluminescence is a phenomena which occurs in certain materials from the passage of an electric current through the material. The electric current excites the electrons of the dopant in the light emitting material to higher energy levels. Emission of radiation thereafter occurs as the electrons emit or give up the excitation energy and fall back to lower energy levels. Such electrons can only have certain discrete energies. Therefore, the excitation energy is emitted or radiated at specific wavelengths depending on the particular material.
Thin film electroluminescent (TFEL) devices that employ the above-mentioned electroluminescence phenomena have been devised in the prior art. It is well known to utilize a TFEL device to provide an electronically controlled, high resolution light source. One arrangement which utilizes the TFEL device to provide the light source is a flat panel display system, such as disclosed in Asars U.S. Pat. No. (4,110,664) and Luo U.S. Pat. No. (4,006,383), assigned to the assignee of the present invention. In a TFEL flat panel display system, light emissions are produced substantially normal to a face of the device and so provide the light source at the device face. Another arrangement utilizing the TFEL device to provide the light source is a line array, or edge, emitter, such as disclosed in a Kun U.S. Pat. No. (4,535,341), also assigned to the assignee of the present invention. In a TFEL edge emitter system, light emissions are produced substantially normal to an edge of the device and so provide the light source at the device edge. A printer is disclosed in the Kun et al patent which employs a TFEL edge emitter device as the light source.
It is known in the prior art to provide the TFEL device either as a face emitter structure for applications requiring a large area light source, such as a flat panel display, or as an edge emitter structure for applications requiring only a narrow light source, such as a light-activated printer. However, unknown in the prior art is an integrated structure which provides the TFEL device as both face and edge emitter devices suitable for applications which heretofore have been assumed to require separate components.